Fix behaviour of listeners in the InventoryService

Fix behaviour of listeners in the InventoryService

Currently a random OVSDB Inventory Listener will be resolved from the
OSGi Service Registry. This commit enables ALL registered inventory
listeners to receive updates using the OSGi Whiteboard Pattern

Additionally there was a hack in the Port and Network Handlers that
created InventoryService events, breaking the Provider/Consumer
contract. This is also fixed in this commit.

Fixes bug 1298

Change-Id: Iec1871a9022291b222a56cbb03e2093d3d45cc7a
Signed-off-by: Dave Tucker <djt@redhat.com>